In 2003, seeds of Macrobrachium rosenbergii were stocked at 2, 4, and 6 postlarvae/m2 as well as 1, 2 and 3 juveniles/m2 with two culture systems, the integrated and rotational prawn - rice systems. Prawns were fed with pellets twice a day. Water levels in rice plots were arranged at the same levels for both systems. The dissolved oxygen concentrations in the integrated system were lower than in the rotational system. The growth of prawns decreased at higher stocking densities. Prawns in the rotational system grew faster than those in integrated system. The yields ranged from 286 ± 32 to 516 ± 51 and 412 ± 17 to 584 ± 37 kg/ha in the integrated and rotational system at stocking PL, respectively. The yields of prawns ranged from 251 ± 16 to 430 ± 54 and 297 ± 24 to 486 ± 38 kg/ha in integrated and rotational prawn - rice systems stocking juveniles, respectively. However, at higher density, the investment cost significantly increased (P < 0.05), while profit significantly decreased (P < 0.05). At low density, cost benefit ratio and profit were the highest (P < 0.05). Finally, the integrated rice - prawn system gives lower profits than the rotational system. In 2004, an experiment on the effects of stocking densities (1, 2, 3 and 4 PL/m2) and feeding types, pellets only (P) and pellets + snail meat (PS), on the production and economic aspects of rotational prawn culture in the rice fields were carried out in the same culture facilities. Water levels were 0.3 - 0.6 m in rice-grown areas. Water temperatures were higher than the suitable range for prawns at noon in the hot months. After 7 months, survival rates of prawns were 28.0 - 50.3 %. Final mean weights were 32.0 - 39.8 g/prawn. Yields ranged from 194 ± 82 to 373 ± 32 kg/ha. There was no significant difference between the two types of feeding on production parameters (P > 0.05). The total cost significantly increased at higher densities (P < 0.05) but it was not different between feed types (P > 0.05). Net profit and cost benefit ratio of treatment PS were significantly higher than in treatment P. In the present study, yield (394 ± 22 kg/ha) and cost benefit ratio (1.57 ± 0.07) in treatment PS at 3 PL/m² were significantly the highest (P < 0.05). The effects of stocking densities of postlarvae (0.5, 1 and 2 PL/m2) on the production and economics of prawn culture in the integrated rice - prawn system were studied to affirm the efficiency of this model with low investment. The high temperature in the dry season and low dissolved oxygen after rice harvesting caused small final mean weights, low survival rates and low yields. However, low investment in this system led to good cost benefit ratio. The on farm trials of rotational rice - prawn farming in the semi-deep water area were monitored with the farmers in six rice fields (0.7 - 1.0 ha). Two treatments of feed types (pellets and pellets + snail meat) were applied at stocking 4 PL/m2. Prawns in two treatments of densities (4 and 5 PL/m2) were fed on a combination of pellets and snail meat. By cull harvesting during the culture period, final mean weights of prawn were improved and larger than 50 g/prawn in all treatments. The prawn yield of treatment 5 PL/m2 was highest (630 ± 22 kg/ha). Net profits in the treatment using a combination of pellets and snail meat were 861 ± 193 US$/ha to 1,019 ± 25 US$/ha for the prawn crop and 1,393 ± 71 US$/ha to 1,576 ± 180 US$/ha for the whole system (prawn crop + dry rice crop). The integrated two rice crop and one prawn crop system with low investment costs can be applied by poor farmers, while the rotational a rice crop and one prawn crop system with higher operating costs can be practiced by moderately well off and rich farmers. Due to a higher economic return than monoculture of rice or rice - fish systems, rice - freshwater prawn system is spreading very rapidly in the Mekong Delta of Vietnam. En 2003, de jeunes Macrobrachium rosenbergii furent stockés à 2, 4 et 6 postlarves/m² ainsi qu’à 1, 2 et 3 juvéniles/m² dans deux systèmes de culture: riz et crevettes produits soit en même temps (intégration) soit successivement (rotation). Les crevettes étaient alimentées de granulés deux fois par jour. Les niveaux d’eau dans les casiers rizicoles ont été maintenus identiques dans les 2 systèmes. Les concentrations en oxygène dissous dans le système intégré étaient plus faibles que dans le système en rotation. La croissance des crevettes a diminué aux plus fortes densités. Les crevettes dans le système en rotation ont grandi plus rapidement que dans le système intégré. Les récoltes à partir de postlarves se sont étalées de 286 ± 32 à 516 ± 51 et de 412 ± 17 à 584 ± 37 kg/ha respectivement dans le système intégré et en rotation. Les récoltes à partir de juvéniles se sont étalées de 251 ± 16 à 430 ± 54 et de 297 ± 24 à 486 ± 36 kg/ha respectivement dans le système intégré et en rotation. Cependant, à plus forte densité, les coûts d’investissement augmentent significativement (P < 0,05), tandis que le profit diminue significativement (P < 0,05). A faible densité le rapport coûtbénéfice et le profit ont été les plus élevés (P < 0,05). Finalement, le système intégré riz-crevette donne des profits plus faibles que le système en rotation. En 2004, une expérience sur les effets de différentes densités de mise en charge (1, 2, 3 et 4 PL/m²) et des types d’aliments, granulés uniquement (G) ou granulés et viande d’escargot (GE), sur la production et les aspects économiques de la culture riz-crevette en rotation ont été effectués dans les mêmes installations que précédemment. Les niveaux d’eau ont varié de 0,3 à 0,6 m dans les zones de production du riz. Les températures de l’eau ont été plus élevées que la température optimale pour la crevette du moins à midi pendant les mois les plus chauds. Après 7 mois, les taux de survie ont été de 28,0 à 50,3 %. Les poids moyens finaux étaient de 32,0 à 39,8 g/crevette. Les récoltes s’étalaient entre 194 ± 82 à 373 ±32 kg/ha. Aucune différence statistique (P < 0,05) concernant les paramètres de production n’a été enregistrée entre les deux types d’alimentation. Les coûts totaux ont augmenté significativement (P < 0,05) à plus fortes densités de mise en charge mais n’étaient pas différents selon les types d’aliments. Le profit net et le rapport coût bénéfice ont été significativement plus élevés avec les aliments combinés (GE) qu’avec les granulés seuls (G). Nos travaux démontrent que la récolte (394 ± 22 kg/ha) et le rapport coût bénéfice du traitement aliment combiné (GE) à 3 PL/:m² donne les meilleurs résultats (P < 0,05). Les effets de différentes densités de mise en charge de postlarves (0,5, 1 et 2 PL/m²) sur la production et le gain monétaire de l’élevage de crevette d’eau douce dans le système riz –crevette intégré ont été étudiés afin de confirmer l’efficacité de ce modèle basé sur un faible investissement. La température élevée en saison sèche et les faibles concentrations en oxygène dissous de l’eau après la récolte du riz induisent des poids moyens finaux faibles, de faibles taux de survie et de faibles récoltes. Cependant, le faible investissement nécessaire conduit à un bon rapport coût bénéfice. Les essais sur fermes du système riz-crevette en rotation dans les zones semi-profondes du district de Codo ont été effectués de façon participative avec les fermiers dans six champs de riz (0,7-1,0 ha). Deux types d’aliments (G et GE) ont été testés à la densité de 4 PL/m² et deux types de densité (4 et 5 PL/m²) ont été testés avec l’aliment combiné (GE). Grâce à des récoltes partielles en cours de production, les poids moyens finaux des crevettes ont été améliorés et étaient supérieurs à 50 g/crevette pour tous les traitements. La récolte de crevette à 5 PL/m² a été la plus élevée (630 ± 22 kg/ha). Les profits nets du traitement combinant les 2 types d’aliments (GE) ont varié de 861 ± 193 US$/ha à 1.019 ± 25 US$/ha pour la récolte de crevettes et de 1.393 ± 71 US$/ha à 1.576 ± 180 US$/ha pour l’ensemble du système (riz + crevette). Le système intégré de deux récoltes de riz et 1 récolte de crevette par an nécessite peu d’investissement et peut être appliquée par les fermiers les plus pauvres tandis que le système une récolte de riz et une récolte de crevette en rotation par an nécessite des investissements plus conséquents et ne peut être appliqué que par des fermiers aisés ou riches. Etant donné que le revenu économique du système riz-crevette est nettement plus élevé que la seule riziculture ou même que la rizipisciculture, ce système est en train de se développer très rapidement dans le delta du Mékong.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of this project was to investigate the impact of different pesticides used in the ricefield on the density and diversity of benthic organisms. In the experiment, two collects of soil were made to identify and quantify benthic organisms, one in the 28th and other in the 84th days after the entry of water in the ricefield. We used a cylindrical collector of PVC (Curer) with 0.10 m in diameter (0.01 m2) at a depth of 0.10 m. Samples were collected in the irrigated plots that received the following treatments: TO - Imazethapyr + Imazapic (ONLY ®), TB - Bispyribac-sodium (NOMINEE 400SC), TQ - Quinclorac (FACET PM), TF - Fipronil (STANDACK) and TC - control. The number of replicates for each treatment was 12 samples per day. The collected material was stored in plastic bags and taken to the laboratory, where it was washed in sieves of 0.25 mm and re-packed in plastic bottles and then immediately stained (Rose-Bengal), and fixed with absolute ethanol. After fixing, the organisms were separated and identified to the lowest taxonomic level possible, using specialized bibliographies. Throughout the period of ricefield, data on the following parameters of irrigation water were recorded: dissolved oxygen, pH, temperature, alkalinity, hardness, turbidity, conductivity and persistence of pesticides used. To verify differences in the physical-chemical, between treatments, we used a TWO-WAY-ANOVA (treatment and time) and a PCA. An ANOVA one criterion was used to verify differences in taxa between treatments and a MANOVA was used to examine differences in fauna composition between treatments and trophic guilds. There were no differences among abiotic data and the treatment, but differences were found in the time of cultivation. Concerning the persistence of pesticides, the herbicide quinclorac was the most persistent, detected up to the 84th day. The lower persistence of the herbicide ONLY® was detected until the 21st day. In the first sample a total of 1971 animals was collected from all treatments, separated into four phyla: Arthropoda (Insecta, Arachnida and Crustacea), Mollusca (Gastropoda), Anellida (Oligochaeta and Hirudinea) and Nematoda. In the second group of samples, 2295 individuals were identified among all treatments. The same phyla were present, but the diversity of insects was higher than in the previous collection. The MANOVA showed differences between the fauna composition of the treatments evaluated, and between collections, as well as among the fauna composition of the same trophic guild in the different treatments. Based on these results we conclude that the pesticides did not affect the physical and chemical parameters of water, however, these products can cause stress on the benthic community at the beginning of culture for a period of approximately one month after the entry of water in the plots. This effect is reduced over time so that the benthic community tends to restructure after the period of greatest activity of pesticides in water. / O objetivo deste estudo foi investigar o impacto da utilização de diferentes agroquímicos, empregados na lavoura de arroz irrigada por inundação, sobre a densidade e riqueza de organismos bentônicos. No experimento, foram realizadas duas amostragens de solo para identificar e quantificar organismos bentônicos, uma no 28º e outra no 84º dia após a entrada de água na lavoura. Utilizou-se um coletor cilíndrico de PVC (Corer) com 0,10 m de diâmetro (0,01 m2) na profundidade de 0,10 m. As amostragens foram realizadas em parcelas que receberam os seguintes tratamentos: TO -imazethapyr + imazapic (ONLY®); TB - bispyribac-sodium (NOMINEE 400SC); TQ - quinclorac (FACET PM); TF - fipronil (STANDACK) e TC - controle. O número de réplicas para cada tratamento foi de 12 amostras por dia amostral. O material coletado foi armazenado em sacos plásticos e levado para o laboratório, onde foi lavado em peneiras de 0,25mm, reacondicionado em frascos plásticos e logo em seguida corado (Rosa-de-Bengala) e fixado com álcool etílico absoluto. Após a fixação os organismos foram triados e identificados até o menor nível taxonômico possível, utilizando-se bibliografias especializadas. Durante todo o período da cultura do arroz foram registrados os dados dos seguintes parâmetros da água de irrigação: Oxigênio dissolvido, pH, temperatura, alcalinidade, dureza, turbidez, condutividade e persistência dos pesticidas utilizados. Para verificar diferenças quanto aos fatores físico-químicos, entre os tratamentos, utilizou-se uma ANOVA de dois critérios (tratamento e tempo) e uma PCA. Uma ANOVA de um critério foi utilizada para verificar diferenças dos táxons entre os tratamentos e uma MANOVA foi empregada para analisar diferenças na composição da fauna entre os tratamentos e guildas tróficas. Não se observou diferenças nos dados abióticos em relação aos tratamentos, mas sim em relação ao tempo de cultivo. Com relação à persistência dos pesticidas, o herbicida Quinclorac foi o mais persistente, detectado até o 84º dia. A menor persistência foi do herbicida Only, detectado até o 21º dia. Na primeira amostragem foram coletados um total de 1971 organismos entre todos os tratamentos, pertencentes a quatro filos: Arthropoda (Insecta, Arachnida e Crustacea), Mollusca (Gastropoda), Anellida (Hirudinea e Oligochaeta) e Nematoda. Na segunda coleta foram identificados 2295 organismos entre todos os tratamentos. Os mesmos filos estiveram presentes, porém a riqueza de insetos foi maior que na coleta anterior. A Manova mostrou haver diferenças entre as composições da fauna dos tratamentos avaliados, e entre as coletas, bem como na composição da fauna, de uma mesma guilda trófica, nos diferentes tratamentos. Com base nestes resultados é possível concluir que os pesticidas utilizados não afetaram os parâmetros físico-químicos da água, entretanto, esses produtos podem causar estresse na comunidade bentônica no início da cultura, por um período de aproximadamente um mês após a entrada de água nas parcelas. Este efeito é reduzido com o passar do tempo, de maneira que a comunidade bentônica tende a se reestruturar após o período de maior ação dos pesticidas na água.

The modern productive relations aim at updating, qualifications and competitiveness towards the competition imposed by the capitalism and the dynamic presented in the production and commercialization relations that, somehow, also influences the agricultural sector imposing new behaviors, patterns and dependencies. This work aims to analyze and discuss the organization of the rice culture in the city of Agudo, RS. In order to do that, the starting point is the conception of a networking area to understand how the integration between sections involved in the production, processing and trade process of rice happens, as well as in the previous steps related to the production process (financing, industry to agriculture, etc.) The methodology used in the development of this work was the collection of data through questionnaires, interviews, informal conversations, photos, statistics and census. Even though the family agriculture is maintained as productive basis, highly dependent of public politics, some sectors of this activity were specialized, maintaining strong relations with each other and assuring its importance in the local market. To make this possible, it was provided a great stimulus through financings and loans, empowering the bonds between growers and processing industries, which broadened their action market through investments in infra-structure and technology. The spatial relations have become more complex when transposing the territories through intersectorial flows. / As modernas relações produtivas buscam atualização, qualificação e competitividade frente à concorrência imposta pelo sistema capitalista em vigor e à dinâmica presente nas relações de produção e comercialização que, de certa forma, influenciam também o setor agropecuário, impondo novas condutas, padrões e dependências. O presente trabalho tem como objetivo analisar e discutir a forma de organização do espaço rizícola do município de Agudo RS, partindo da concepção de um espaço em rede para entender como ocorre a integração entre os setores envolvidos no processo de produção, beneficiamento e comercialização do arroz, assim como nas etapas anteriores ao processo produtivo (financiamentos, indústria para a agricultura, etc). Os processos metodológicos empregados no desenvolvimento do trabalho foram coleta de dados por meio de questionários, entrevistas, conversas informais, fotografias e dados estatísticos e censitários. Embora mantendo a agricultura familiar como base produtiva, fortemente dependente de políticas públicas, manifestou a especialização em setores da atividade, os quais mantêm amplas relações entre si, a fim de assegurar sua expressividade no local. Para que isso fosse possível, houveram grandes incentivos através de financiamentos e empréstimos, aprofundando os vínculos entre produtores rurais e indústrias de beneficiamento, e estas por sua vez ampliaram seu mercado de atuação através dos investimentos em infra-estrutura e tecnologia. As relações espaciais adquiriram maior complexidade ao transpor os territórios através de fluxos intersetoriais.

O presente estudo aborda a importante questão ambiental, muito discutida nos tempos atuais. O eixo de discussão enfatiza o contexto do impacto sócio-ambiental e sua previsão quanto às fases de realização e operação de empreendimentos hidroelétricos. O direcionamento da discussão trata, dentre outras circunstâncias, do entorno da barragem hidrelétrica Xingó passível de conseqüências, como o município de Porto da Folha/SE à margem do rio São Francisco. Para melhor contextualizar o episódio, versa-se, inicialmente, da geo-história e da natureza do lugar descrevendo-as de forma a evidenciar importantes ocorrências desde denominações local e regional até o espaço físico no ciclo do arroz. Depois, destaca-se a dinâmica natural na abordagem dos aspectos físico-naturais em conjunto com a dinâmica fluvial do São Francisco. O ciclo da cultura de arroz, quando e como das cheias e vazantes, engendrava o modo da comunidade ribeirinha sobreviver, assim, resultando a relação homem-natureza no lugar. Além disso, salienta-se a ligação dos traços culturais locais com o ciclo do arroz. Por fim, analisando o poder do Estado, no sistema democrático, foi avaliado o conjunto de ações governamentais em termos de efetividade e eficácia. Tal avaliação abrange tanto as políticas de mitigação dos impactos causados pelo controle de vazão do rio quanto a fiscalização sobre o sistema de meação. / This study is about the important environmental issue widely discussed in recent times. The central part of the discussion emphasizes on the context of the socioenvironmental impact and the forecasting regarding the realization and operation steps of hydroelectric developments. The direction of the discussion is about, amongst other circumstances, the surroundings of the Xingó hydroelectric plant passive of consequences, such as the city of Porto da Folha/SE located by the banks of the river São Francisco. To better contextualize the episode, the study initially refers to geo-history and the natural aspects of the place, describing them in a way to highlight important events, from local and regional denominations to the physical space in the rice cycle. Afterwards, the natural dynamics is highlighted in the discussion of physic-natural aspects along with the flow dynamics of the river São Francisco. The rice cycle, when and how the level of the river was high or there was flooding formed the way the riverside population survived, eventually resulting in the mannature relation in that place. Furthermore, it emphasizes on the connection between the local cultural aspects with the rice cycle. In the end, by analyzing the power of the state in the democratic system, it was evaluated the collection of governmental actions in terms of efficiency and effectiveness. Such evaluation includes from mitigation policies of the impacts caused by the flooding control to the supervision of halving system.

O presente estudo aborda a importante questão ambiental, muito discutida nos tempos atuais. O eixo de discussão enfatiza o contexto do impacto sócio-ambiental e sua previsão quanto às fases de realização e operação de empreendimentos hidroelétricos. O direcionamento da discussão trata, dentre outras circunstâncias, do entorno da barragem hidrelétrica Xingó passível de conseqüências, como o município de Porto da Folha/SE à margem do rio São Francisco. Para melhor contextualizar o episódio, versa-se, inicialmente, da geo-história e da natureza do lugar descrevendo-as de forma a evidenciar importantes ocorrências desde denominações local e regional até o espaço físico no ciclo do arroz. Depois, destaca-se a dinâmica natural na abordagem dos aspectos físico-naturais em conjunto com a dinâmica fluvial do São Francisco. O ciclo da cultura de arroz, quando e como das cheias e vazantes, engendrava o modo da comunidade ribeirinha sobreviver, assim, resultando a relação homem-natureza no lugar. Além disso, salienta-se a ligação dos traços culturais locais com o ciclo do arroz. Por fim, analisando o poder do Estado, no sistema democrático, foi avaliado o conjunto de ações governamentais em termos de efetividade e eficácia. Tal avaliação abrange tanto as políticas de mitigação dos impactos causados pelo controle de vazão do rio quanto a fiscalização sobre o sistema de meação. / This study is about the important environmental issue widely discussed in recent times. The central part of the discussion emphasizes on the context of the socioenvironmental impact and the forecasting regarding the realization and operation steps of hydroelectric developments. The direction of the discussion is about, amongst other circumstances, the surroundings of the Xingó hydroelectric plant passive of consequences, such as the city of Porto da Folha/SE located by the banks of the river São Francisco. To better contextualize the episode, the study initially refers to geo-history and the natural aspects of the place, describing them in a way to highlight important events, from local and regional denominations to the physical space in the rice cycle. Afterwards, the natural dynamics is highlighted in the discussion of physic-natural aspects along with the flow dynamics of the river São Francisco. The rice cycle, when and how the level of the river was high or there was flooding formed the way the riverside population survived, eventually resulting in the mannature relation in that place. Furthermore, it emphasizes on the connection between the local cultural aspects with the rice cycle. In the end, by analyzing the power of the state in the democratic system, it was evaluated the collection of governmental actions in terms of efficiency and effectiveness. Such evaluation includes from mitigation policies of the impacts caused by the flooding control to the supervision of halving system.